Synthesis of unsaturated hydrocarbons from unsaturated ketones



United States Patent Ofifice 2,693,497 Patented Nov. 2, 1954 SYNTHESISOF UNSATURATED HYDROCAR- BONS FROM UNSATURATED KETONES Seaver A.Ballard, Orinda, Harry De V. Finch, El Cerrito, and Elbert A. Peterson,Berkeley, Calif., assignors to Shell Development Company, San Francisco,Calif a corporation of Delaware No Drawing. Application October 14,1949, Serial No. 121,448

11 Claims. (Cl. 260-681) This invention relates toa process forthesynthesis of unsaturated hydrocarbons. More particularly, the presentinvention relates to a process for the direct synthesis of unsaturatedhydrocarbons, particularly diene hydrocarbons, which involves "reactionof an unsaturated ketone with an alcohol in the vapor phase in thepresence of a catalyst. The application is a continuation-in-part of ourallowed copending application, Serial No. 700,368, filed October 1,1946, now U. S. Patent No. 2,492,956, issued January 3, 1950, whichapplication is in turn a continuation-in-part of our application SerialNo. 669,110, filed May 1 1, 1946, now abandoned, application Serial No.669,110 being in turn a continuation-in-part of our pending application,Serial No. 633,860, filed December 8, 1945, now abandoned. The inventionto which the present application is directed concerns a process for thedirect synthesis of unsaturated hydrocarbons that is characterized inpart by the particular catalysts that are used for effecting thesynthesis, the catalysts of this invention being especially advantageousfor the reasons, among others, that they are efficient, easy to prepare,highly economic, and serve for the direct synthesis of the desiredunsaturated hydrocarbons in a desirably high state of purity.

It is known that certain unsaturated hydrocarbons, especially butadiene,can be prepared by reacting suitable olefinic aldehydes, particularlycrotonaldehyde, with non-tertiary alcohols in the vapor phase in thepresence of particular catalysts. Low yields, not over 25%, of butadienehave been described as resulting from the reaction under suitableconditions of crotonaldehyde and ethanol in the'presence of precipitatedaluminum hydroxide. More recently, there have been reported results ofexperimentsdesigned to improve the synthesis of butadiene fromcrotonaldehyde bythe use of certain other catalysts, such as pure silicagel and zirconium oxide, tantalum oxide, columbium oxide andcombinations of these oxides with silica.

The processes known prior to our' invention have been generally lesssatisfactory for the production of unsaturated hydrocarbons by reactionin the vapor phase between unsaturated ketones and alcohols. In ourexperiments, we have found that the reaction of mesityl oxide, arepresentative unsaturated ketone which is useful in the process of thepresent invention, with isopropyl alcohol over pure silica gel, acatalyst that is representative of those employed in the prior art,leads to undesirably low yields of methyl pentadienes. Unlike theunsaturated aldehydes that have been employed for the preparation ofunsaturated hydrocarbons in the prior art, the unsaturated ketones,particularly the aliphatic and cycloaliphatic unsaturated ketonescontaining at least six carbon atoms, appear to be especially prone toundergo reactions other than the reaction or reactions leading to thedesired unsaturated hydrocarbon. As a result, there is encounteredexcessive formation of products other than the desired unsaturatedhydrocarbon, or else there is reaction (of any kind) to such a slightdegree that only negligible formation of desired product is obtained inour allowed copending application, Serial No. 700,368, acknowledgedabove, there is disclosed and claimed a process for the preparation ofunsaturated hydrocarbons, especially dienes, from alpha,beta-olefiui ketn ontain n atrleast carbon, atoms wh ch to the carbon atom of thecarbonyl group.

is characterized in part by the use of catalysts comprising adsorptivealuminas comprising alumina alpha monohydrate, gamma alumina, ormixtures thereof, and a cobalt and/or a copper oxide. The invention towhich the present application relates concerns a process for thepreparation of unsaturated hydrocarbons, especially dienes, fromunsaturated ketones, particularly alpha,beta-olefinic ketones containingat least six carbon atoms, presumably involving the same generalreaction or reactions, but characterized in part by the use of anothergroup of particular catalysts or types of catalyst.

The catalysts that are employed in accordance with the process of thepresent invention are solid catalysts comprising at least one oxide ofan element of group II of the periodic table of the elements. It hasbeen found that solid catalyst masses comprising at least one oxide of agroup II metal are highly effective for the conversion of unsaturatedketones to unsaturated hydrocarbons by reaction with alcohols accordingto the process disclosed, and that with the aid of such catalysts goodconversions to and yields of the desired product can be obtained. Ascatalysts for the desired reaction, catalysts comprising oxides ofelements of group II of the periodic table of the elements have theadvantage that they are easily prepared from materials that in manycases are available at negligible cost. The catalysts of the presentinvention have the further advantage that they promote minimalconversion of the unsaturated ketone or alcohol reactants to low-boilingor gaseous by-products. In other words, the catalysts which characterizethe process of the present invention lead to little, if any,decomposition of the organic materials which are present to materials ofsubstantially lower molecular weight. Another and particular advantageof the catalysts which are employed according to the present inventionis the prolonged period of time over which they may be continuouslyemployed without need for replacement or regeneration. As a result,desirably high conversions of the unsaturated ketone reactant per unitamount of catalyst are obtainable in accordance with the process of theinvention.

The process of the present invention may be applied generally to theconversion to unsaturated hydrocarbons, of ketones that contain at leastsix carbon atoms and an unsaturated linkage of aliphatic characterbetween two carbon atoms one of which is directly linked Although theunsaturated linkage may be either olefinic in character or acetylenic incharacter, particularly desirable results are obtained when thealpha,beta-unsaturated linkage is olefinic in character. By reference toan unsaturated linkage of aliphatic character, we intend to include notonly an olefinic linkage between two aliphatic carbon atoms, but, aswell, an olefinic linkage between two carbon atoms which are in acycloaliphatic ring, since it is well-known that the latter type oflinkage has many of the characteristics of a strictly aliphaticunsaturated linkage.

The unsaturated ketones which may be employed in accordance with theinvention contain a linear group may be symmetrical or unsymmetrical andthey may be acyclic or cyclic. They may contain one or more aromaticgroups. Particularly advantageous results are obtained when the ketoneis a non-aromatic ketone. Representative mono-olefinic ketones are, forexample, mesityl oxide, homomesityl oxide, isopropyl isopropenyl ketone,butyl isopropenyl ketone, isobutyl isopropenyl ketone, ethyl isopropenylketone, and their various homologs and analogs. Suitable cyclic ketonesinclude, among others, 3,5,5 trimethyl 2 cyclohexen-l-one (isophorone),2- cyclohexen-l-one, Z-methylcyclopenten-l-one, 3-ethyl-2-cyclohexen-l-one, 2,3-dimethyl-2-cyclohexen-l-one,2-isopropylidene-l-cyclohexanone, 2-isobutylidene-3-methyl-1-cyclohexanone, l-acetal-l-cyciohexene, 1acetal-2-methyll-cyclohexene,and their various analogs and homologs. Ketones, such as allyl vinylketone, diisopropenyl ketone,

4-isopropenyl-2-cyclohexen-l-one, 3-isopropenyl-4-ethyl-2-cyclohexen-l-one, which will be seen to contain a plurality of olefiniclinkages, may be employed to prepare unsaturated hydrocarbons containingmore than two olefinic linkages. The unsaturated ketones which may beutilized in the process of the invention may contain a plurality ofcarbonyl groups, as in diketones and ketoaldehydes. They may alsocontain substituents provided such substituents are not of a kind and/or in a position in the molecule to interfere with the successfulpractice of the process of the invention. The process of this inventionis especially suited to the preparation of unsaturated hydrocarbons ofthe herein-defined class from ketones that contain an olefinic linkageas the only carbon-to-carbon unsaturation, and that preferably containfrom six to twelve carbon atoms. Because of the especially valuablenature of the unsaturated hydrocarbons (methylpentadienes) synthesizedtherefrom, mesityl oxide is an unsaturated ketone of particularinterest. Other particularly useful hydrocarbons may be preparedaccording to the process from isophorone and homomesityl oxide.

In accordance with the process of the invention, a ketone of theherein-defined class is reacted with a nontertiary, preferably saturatedalcohol in the presence of a solid catalyst comprising an oxide of ametal of group II of the periodic table of the elements to directlyproduce an unsaturated hydrocarbon containing the same number of carbonatoms as the ketonic reactant. Suitable non-tertiary alcohols arealcohols that contain at least one hydroxyl group and that have at leastone atom of hydrogen directly linked to the carbon atom to which thehydroxyl group is bonded. The lower non-tertiary alkanols, e. g.,methanol, ethanol, propanol, isopropanol, butanol, isobutanol, and theirsuitable homologs are highly satisfactory and have the added, obviousadvantage of low cost. More generally speaking, the alcohol may be anysuitable non-tertiary alcohol, and may be saturated or unsaturated,cyclic or acyclic. Other alcohols which may be employed in accordancewith the more generic aspects of the invention include, among others,allyl alcohol, methyl vinyl carbinol, benzyl alcohol, benzyl carbinol,cyclohexanol, trimethylene glycol, and the like and their varioushomologs and analogs. Among the various alcohols, isopropanol isparticularly preferred, especially when mesityl oxide is the unsaturatedketonic reactant. The isopropanol is converted in the execution of theprocess to acetone. The acetone may be recovered and in turn may beconverted by known methods to an additional amount of mesityl oxide.

The catalysts which are employed in accordance with and whichcharacterize the process of the present invention contain as anessential component at least one oxide of a metal of group II of theperiodic table of the elements. One or a plurality of such oxides may beused in the substantially pure state. Even higher conversions of theunsaturated ketone reactant to desired unsaturated hydrocarbon producthave been observed when, in addition to the oxide(s) of group II metalsthe catalyst comprises an additional substance havinghydrogenationdehydrogenation activity. This type of catalyst is employedin accordance with the more highly preferred aspects of the invention.

As examples of oxides of elements of group II of the periodic table ofthe elements, which may be employed alone or in admixture as thecatalyst in accordance with the invention, there are the oxides of themetals of the main group of group II of the periodic tables, theseoxides including beryllium oxide, magnesium oxide, calcium oxide,strontium oxide and barium oxide. Zinc oxide and cadmium oxide, whichare heavy metals of group II, are also included. The oxides of themetals of group II having atomic numbers less than 80 are particularlycontemplated. Mixtures of oxides of metals of group II which may beemployed as catalysts in the execution of the process of the inventioninclude binary, ternary, as well as even quaternary or higher mixtures,examples of suitable mixtures being oxides of calcium and magnesium, ofmagnesium and zinc, of calcium and zinc, of beryllium and zinc, ofcalcium, magnesium, and zinc, of strontium and calcium, of beryllium,strontium and zinc, and of zinc and barium. Particularly preferredcatalysts containing a plurality of oxides of metals of group II arethose which contain as one of the oxides the oxide of zinc, preferablyin a predominating amount (mole basis) based upon the other oxide oroxides of group II element(s) present, preferably in conjunction with anoxide of an alkaline earth metal, such as calcium or magnesium,catalysts containing zinc oxide having been found to result in higheryields of the desired unsaturated hydrocarbons than the catalysts of thepresent invention that do not contain zinc oxide:

When, as is preferred, the oxide or oxides of the metal(s) of group IIof the periodic table of the elements is or are employed in conjunctionwith a material that is an active hydrogenation-dehydrogenationcatalyst, such material may be, for example, copper, iron, magnetite,iron oxide, alumina, chromium oxide, thoria, copper chromite, and likesubstances of the class generally known as and referred to by thoseskilled in the art as hydrogenationdehydrogenation catalysts. When sucha mixture of two or more substances comprises the catalyst, thesubstances generally may be present in any suitable proportion. Aparticularly valuable catalyst is one containing zinc oxide, or zincoxide and a lesser amount of an alkaline earth metal oxide, supportedupon an activated alumina, the oxides of zinc and the alkaline earthmetal preferably being present in a mole ratio within the range of fromabout 1:1 to about 20:1. Catalysts comprising a minor amount, preferablyfrom about 2% to about 45% by weight, of an oxide of a metal of group IIof the periodic table of the elements or a mixture of oxides of metalsof group II of the periodic table of the elements, and a majorproportion of an activated alumina, are especially suited to the objectsof the invention.

The activated aluminas which are employed in ac cordance with oneembodiment of the invention are adsorptive aluminas, which comprisepredominantly alumina alpha monohydrate, gamma alumina, or mixtures ofalumina alpha monohydrate and gamma alumina, which adsorptive aluminamay or may not contain minor proportions of another oxide of anamphoteric element, e. g., ferric oxide. The aluminas that arecharacterized by their active adsorptive characteristics are obtainablefrom various natural sources or they may be prepared by known syntheticmethods. An efficient and inexpensive activated or adsorptive aluminacan be prepared by treatment, or calcination of selected natural bauxiteores. Activated or calcined bauxites, as well as adsorptive aluminashaving the same general physical and chemical characteristics asactivated or calcined bauxites, are particularly suitable for use inaccordance with the process of the invention. Synthetic adsorptivealuminas can be prepared according to known methods from gels, which maybe peptized or unpeptized, or preferably from the crystalline form, suchas the crystalline alpha alumina trihydrate crystallized from alkalialuminate solutions. Various methods for preparing activated oradsorptive aluminas are well-known and will be apparent to those skilledin the art.

The catalyst which is employed in accordance with the present inventionmay be in the form of a powder, in the form of pellets or other shapedpieces, in the form of fragments or other particles of regular orirregular contour. The catalyst mass may be self-supporting or it may besupported in or upon an inert or active support, such as pumice, silica,charcoal, kieselguhr, silicon carbide porous aggregates, and the like.In some cases the finely-ground metal oxide or oxides that are toconstitute the catalyst mass conveniently may be worked up with water toa paste, the paste extruded in the form of cylinders of suitable size,and the cylinders dried. Suitable catalysts may be formed by pilling orother operations known to those skilled in the art relating to thepreparation or forming of catalyst masses.

According to a preferred mode of executing the process of the invention,a mixture comprising the unsaturated ketone and the non-tertiary alcoholis contacted in the vaporous state with the solid catalyst comprisingthe oxide or oxides of one or more metals of group II of the periodictable of the elements. Although considerable latitude is permissible,the temperature employed generally is from about 200 C to about 500 C.,a preferred range being from about 200 C. to about 350 C., and aparticularly efiective range, when the catalyst comprises zinc oxide,being between about 250 C. and 340 C. Catalysts comprising zinc oxideand an activated alumina generally can be employed at lower temperaturesthan, for example, magnesia or magnesia-alumina catalysts withsubstantially equivalent results. When the catalyst is or essentiallycomprises magnesium oxide, temperatures higher than those most suitablefor the zinc oxide catalysts are preferred, e. g., about 375 C. to 475C. The non-tertiary alcohol preferably is employed in excess, on a molebasis compared to the unsaturated ketone, mole ratios of (non-tertiaryalcohol):(unsaturated ketone) of from 1:1 to :1 being generally suitableand such ratios of from 2:1 to 6:1 being preferred. Inert diluent gases,although the presence thereof is ordinarily neither required norpreferred, may be included in the gaseous mixture which is contactedwith the catalyst. It is desirable to conduct the process undersubstantially anhydrous conditions. The presence of molecular hydrogenis not required for accomplishing the objects of the invention. The useof substantially atmospheric pressures is generally most convenient;however, the process may be conducted under subatmospheric orsuperatmospheric pressures.

When, as is preferred, the process is carried out in a continuousmanner, any type of apparatus suitable for use in catalytic vapor phasereactions of the present type may be employed. When the catalyst isemployed as a fixed bed, as is preferred, the bed of the catalyst may bepositioned in a suitable chamber, such as a heated elongated tube, and agaseous mixture of the selected reactants passed therethrough undersuitable conditions of temperature, pressure, proportions of thereactants, and rate of flow. The rate of flow to be used with mostadvantage in any particular case is determined to a certain extent bythe particular reactants that are involved, by the nature of thecatalyst, the temperature, and the related reaction conditions. In eachcase, the several reaction conditions may be correlated to obtainoptimum conversion of the unsaturated ketone to the desired unsaturatedhydrocarbon. In general, the rate of flow, which expressed numericallyas equal to the total number of moles of the reactants contacted with100 cc. of the catalyst per minute, may be within the range of fromabout 0.005 to about 0.10 mole of reactants per 100 cc. of catalyst perminute. More preferably, rates of flow from about 0.02 to about 0.075total mole of reactants per 100 cc. of catalyst are used. In particularcases, rates of how from about 0.04 to about 0.06 are optimum,especially when the catalyst is one that comprises zinc oxide or zincoxide and an activated or adsorbent alu mina, and the temperature isbetween about 250 C and about 340 C., or magnesium oxide and thetemperature is between about 375 C. and 475 C.

The process conveniently is conducted by vaporizing the respectivereactants, the vapors being preheated, if desired, to the reactiontemperature, and passing a gaseous mixture of the vapors through or overa bed of the solid catalyst comprising an oxide of a metal of group IIof the periodic table of the elements. While the catalyst is preferablyused in the form of a fixed bed, fluidized beds of finely dividedcatalyst may be used. It is an advantage of the present catalysts thatthey can be employed for prolonged periods of time without need forregeneration. If carbonaceous, tarry, or like deposits should accumulateon the catalyst after extensive use, such deposits may be removed byinterrupting the process at any convenient time and passing air or othersuitable molecular oxygen-com taining gas through the catalyst bed toburn off undesired organic deposits. Inert gas, such as steam, nitrogenand carbon dioxide, may be present during the regeneration treatment.During the regeneration treatment, the temperature of the catalyst massis maintained at temperatures preferably between about 350 C. and 950C., although in certain cases, when for example, a magnesia-zinc oxidecatalyst is employed, peak temperatures of about 480 C.

during the reactivation are preferable. In any case, temperatures higherthan about 900 C. ordinarily are avoided since they may tend to causeundesired changes in the characteristics of the catalyst and permanentlyaifect its activity.

The products that are obtained from the reaction of thealpha,beta-unsaturated ketones of the herein-defined class withnon-tertiary alcohols in the presence of the catalysts of the inventioncomprise predominantly one or more unsaturated hydrocarbons that containthe same number of carbon atoms per molecule as the unsaturated ketonereactant but that contain more carbon-to-carbon unsaturation than saidreactant. When an unsaturated monolcetone containing analpha,beta-olefinic linkage as the only carbon-to-carbon unsaturation isemployed, the prod uct comprises one or more diene hydrocarbons that contain the same number of carbon atoms .as the unsaturated 6 ketonereactant. Mixtures of such hydrocarbons may be formed, wherein thecomponent unsaturated hydrocarbons diifer by the position(s) of theolefinic linkage(s). The formation of such mixtures appears to be due toa possible isomerization under the conditions of reaction which resultsin a shift in the position of at least one of the unsaturated linkagesof the unsaturated hydrocarbon product. It will be understood that theunqualified terms a methylpentadiene, a diene, or an unsaturatedhydrocarbon, although used in the singular, are intended to include theplural and that the plural forms thereof are intended to include thesingular.

The desired unsaturated hydrocarbon product may be recovered from thereaction products in any convenient suitable manner. In continuousoperation of the process, the gaseous efliuent from the reaction chambercontains the desired unsaturated hydrocarbon product along with anyunreacted unsaturated ketone, non-tertiary alcohol and possibleby-products. The unsaturated hydrocarbon or hydrocarbons produced in theprocess can be separated from the efiluent in any suitable way, such asby fractional distillation of the condensed effluent, by treatment withselective solvents, by chemical means, or the like. Mixtures of isomerichydrocarbons, if produced, can be resolved, for example, by knownchemical or physical methods, it being understood, however, that theprocess of the present invention is not regarded as being limitedaccording to whether or not such subsequent separation of mixtures ofisomeric hydrocarbons is undertaken. Any unreacted unsaturated ketoneand/or nontertiary alcohol present in the efliuent from the reactionzone may be recovered and recycled through the process.

The following examples will illustrate certain of the specificembodiments of the invention. It will be appreciated that the examplesare presented with the intent of illustrating the invention and not as alimitation upon the invention, which is defined in the hereto appendedclaims.

Example I For this experiment, which illustrates use of a zincoxide-activated alumina catalyst, the catalyst was prepared byimpregnating 200 grams of granular activated alumina with an aqueoussolution containing 73 grams of zinc nitrate hexahydrate. Theimpregnated activated alumina was dried and the zinc nitrate wasdecomposed to zinc oxide by heating in air at about 400 C. The catalystcontained about 10% by weight of zinc oxide.

About cc. of the zinc oxide-activated alumina were packed into a steeltube having an inside diameter of about /8 inch and a heated length ofabout 24 inches. A thermocouple well, inch outside diameter, extendedcoaxially through the reactor tube to provide means for measurement ofthe temperature.

The catalyst and tube were heated to and maintained at about 250 C. bymeans of heating elements surrounding the reaction tube. Isopropylalcohol and mesityl oxide were vaporized, the vapors mixed, and a streamof the mixture passed through the tube in a mole ratio of 9.5:] and at arate of flow equal to 0.049 total moles of reactants per 100 cc. of thecatalyst per minute. The pressure was substantially atmospheric. Thegaseous effluent from the reactor was condensed in a water-cooledcondenser and the condensate fractionally distilled. Methylpentadienes,in a purity of about 96%, were recovered in a conversion of appliedmesityl oxide to-product of 62.5 as the fraction distilling betweenabout 74 C. and 76 C.

Example II For this experiment, the catalyst was prepared by finelygrinding in a ball mill a slurry of magnesium oxide, filter ing theslurry, extruding the resulting stifl moist paste in the form of shortcylinders about /s inch in diameter, and drying at C. to C. About 100cc. of the catalyst was used in the apparatus described in Example I.

Isopropyl alcohol and rnesityl oxide were passed in the vapor phase at amole ratio of 6:1 and a rate of flow equal. to 0.049 total mole ofreactants per 100 cc. of the catalyst per minute, over the catalystheated to a temperature of about 460 C. The efiluent was treated as inExample I. for recovery of product. Fifty-two per cent of the mesityloxide feed was converted to methylpentadienes.

Example III Mesityl oxide and isopropyl alcohol were mixed in the vaporstate in a mole ratio of 6:1 and passed at a rate of flow equal to 0.074total mole. per 100 cc. of catalyst per minute, over a fresh portion ofthe catalyst used in the preceding example. The reaction temperature wasabout 460 C. Methylpentadienes were recovered from the effluent from thereaction tube in an amount corresponding to a 44.3% conversion ofmesityl oxide to product.

Example IV In order to compare a catalyst containing zinc oxide with themagnesium oxide catalyst used in the preceding example, a catalystcontaining 10% by weight of zinc oxide and 1% by weight of calcium oxideon activated alumina was prepared by impregnating granular activatedalumina with an aqueous solution of zinc and calcium nitrates, dryingand decomposing the nitrates to the oxides. 7

Isopropyl alcohol and mesityl oxide were vaporized separately and amixture of the vapors in a mole ratio of 6:1 passed over the catalyst ata rate of flow equal to 0.073 total mole per 100 cc. of catalyst perminute, at a catalyst temperature of 370 C. Of the mesityl oxide feed,60% was recovered as methylpentadienes. It will be seen that with theexception of the temperature and the composition of the catalyst, thisexperiment and the one described in the next preceding example weresubstantially the same. The results of this experiment indicate that thecatalyst containing zinc oxide is active at lower temperatures than themagnesia catalyst.

Example V The catalyst was prepared by extruding as in Example I a wetpaste of a finely-ground mixture of 89 parts by weight calcium oxide and11 parts by weight of magnesium oxide, and drying the extrudate. At atemperature of 430 C., passing a gaseous mixture of isopropyl alcoholand mesityl oxide, mole ratio 6:1, over the catalyst at a rate of flowequal to 0.049 mole of reactants per 100 cc. of catalyst per minuteresulted in a 34% conversion of mesityl oxide to methylpentadienes.

Example VI isopropyl alcohol and mesityl oxide were vaporized and passedat a mole ratio of 6:1 and a rate of flow equal to 0.024 total mole ofreactants per 100 cc. of catalyst per minute, over a further portion ofthe catalyst used in Example I, while maintaining the temperature at 250C. Of the mesityl oxide fed, 53.2% was converted to methylpentadienes.

Although in the examples the invention has been illustrated withparticular reference to the preparation of methylpentadienes frommesityl oxide and isopropyl alcohol, it is to be understood that theinvention is not limited according to this particular unsaturated ketoneof the class described hereinbefore, nor to the use of the specificnon-tertiary alcohol. Other non-tertiary alcohols, e. g., ethanol,'butanol, isobutanol, and propanol, can be substituted for theisopropanol. By employing isophorone instead of mesityl oxide,trimethylcyclohexadienes can be prepared. From methyl isopropenylketone, isoprene can be prepared. Homomesityl oxidemethyl-4-hepten-3-one) can be employed for the preparation of octadienesand methyl hexadienes can be prepared from 2-methyl-2-hexen-4-one. Thecatalysts by which the process of the invention is, in part,characterized, may be employed according to the process of the inventionto prepare numerous useful unsaturated hydrocarbons by reactingalpha,beta-unsaturated ketones of the defined class and nontertiaryalcohols.

We claim as our invention:

1. In a process for the preparation of a methylpentadiene by interactionof mesityl oxide and an alcohol, passing a gaseous mixture comprisingmesityl oxide and isopropyl alcohol into contact with a solid catalystessentially comprising zinc oxide and an adsorptive alumina comprisingpredominantly a member of the group consisting of alumina alphamonohydrate, gamma alumina, and mixtures thereof, and recovering amethylpentadiene from the reaction products.

2. In a process for the preparation of a methylpenta' diene byinteraction of mesityl oxide and an alcohol, passing a gaseous mixturecomprising mesityl oxide and isopropyl alcohol into contact with a solidcatalyst essentially comprising zinc oxide at a temperature of fromabout 200 C. to about 500 C. and recovering a methylpentadiene from thereaction products.

3. In a process for the preparation of a methylpentadiene by interactionof mesityl oxide and a lower alkanol having at least one atom ofhydrogen directly linked to the carbon atom to which the hydroxyl groupis bonded the improvement consisting of effecting such interaction bypassing a gaseous mixture comprising said reactants into contact with asolid catalyst essentially comprising zinc oxide, the mole ratio ofmesityl oxide to lower alkanol in said gaseous mixture being within therange of from about 1:1 to about 10: 1, at a temperature within therange of from about 200 C. to about 350 C. and at a rate of flow of fromabout 0.005 to about 0.10 total mole of reactants per cubic centimetersof catalyst per minute.

4. In a process for the preparation of a methylpentadiene by interactionof mesityl oxide and an alcohol having at least one atom of hydrogendirectly linked to the carbon atom to which the hydroxyl group is bondedthe improvement consisting of efiecting such interaction by passing agaseous mixture comprising said reactants into contact with a solidcatalyst essentially comprising an oxide of an element of group II ofthe periodic table of the elements at a temperature within the range offrom about 200 C. to about 500 C. and at a rate of flow of from about0.005 to about 0.10 total mole of reactants per 100 cubic centimeters ofcatalyst per minute.

5. In a process for the preparation of a methylpentadiene by interactionof mesityl oxide and an alcohol having at least one atom of hydrogendirectly linked to the carbon atom to which the hydroxyl group is bondedthe improvement consisting of effecting such interaction by passing agaseous mixture comprising said reactants into contact with a solidcatalyst essentially comprising an oxide of an element of group II ofthe periodic table of the elements at a temperature of from about 200 C.to about 350 C., and recovering a methylpentadiene from the reactionproducts.

6. In a process for the preparation of a diene by interaction of analpha,beta-olefinically unsaturated ketone containing at least sixcarbon atoms and having a linear group of at least four contiguouscarbon atoms joined together by aliphatic carbon-to-carbon bondsincluding the carbon atom of the carbonyl group and a secondary alcoholthe improvement consisting of efiecting such reaction by passing agaseous mixture comprising said reactants into contact with a solidcatalyst essentially comprising zinc oxide at a temperature of fromabout 200 C. to about 350 C., and recovering a diene containing the samenumber of carbon atoms as the alpha,betaolefinically unsaturated ketonefrom the reaction prodnets.

7. In a process for the preparation of a diene by interaction of analpl1a,beta-olefinically unsaturated ketone containing at least sixcarbon atoms and having a linear group of at least four contiguouscarbon atoms joined together by aliphatic carbon-to-carbon bondsincluding the carbon atom of the carbonyl group and an alcohol theimprovement consisting of effecting such reaction by passing a gaseousmixture comprising said reactants having at least one atom of hydrogendirectly linked to the carbon atom to which the hydroxyl group is bondedinto contact with a solid catalyst essentially comprising an oxide of anelement of group II of the periodic table of the elements at atemperature of from about 200 C. to about 500 C. and at a rate of flowequal to about 0.02 to about 0.075 total mole of reactants per 100 cubiccentimeters of catalyst per minute, and recovering a diene containingthe same number of carbon atoms as the alpha,beta-olefinicallyunsaturated ketone from the reaction products.

S. In a process for the preparation of a diene by interaction of analpha,beta-olefinically unsaturated ketone containing at least sixcarbon atoms and having a linear group of at least four contiguouscarbon atoms joined together by aliphatic carbon-to-carbon bondsincluding the carbon atom of the carbonyl group and a secondary alcoholthe improvement consisting of effecting such reaction by passing agaseous mixture comprising said reactants into contact with a solidcatalyst essentially comprising magnesium oxide at a temperature of fromabout 200 C. to about 500 C. and a rate of flow of from about 0.02 toabout 0.075 total mole of reactants per 100 cubic centimeters ofcatalyst per minute, and recovering a diene containingthe same number ofcarbon atoms as the alpha,beta-olefinically unsaturated ketone from thereaction products.

9. In a process for the production of a diene by interaction of analpha,beta-olefinically unsaturated ketone having a linear group of atleast four contiguous carbon atoms joined together by aliphaticcarbon-to-carbon bonds including the carbon atom of the carbonyl groupand a secondary alcohol the improvement consisting of effecting suchreaction by passing a gaseous mixture comprising said reactants intocontact with a solid catalyst essentially comprising zinc oxide at atemperature of from about 200 C. to about 500 C. and at a rate of flowof from about 0.005 to about 0.10 total mole of reactants per 100 cubiccentimeters of catalyst per minute.

10. In a process for the production of a diene by interaction of analpha,beta-olefinically unsaturated ketone having a linear group of atleast four contiguous carbon atoms joined together by aliphaticcarbon-to-carbon bonds including the carbon atom of the carbonyl groupand an alcohol having at least one atom of hydrogen directly linked tothe carbon atom to which the hydroxyl group is bonded the improvementconsisting of effecting such reaction by passing a gaseous mixturecomprising said reactants into contact with a solid catalyst essentiallycomprising an oxide of an element of group II of the periodic table ofthe elements at a temperature of from about 200 C. to about 350 C., themole ratio of said alpha,beta-olefinically unsaturated ketone to saidalcohol in the gaseous mixture being within the range of from about 1:1to about :1, at a rate of flow of from about 0.005 to about 0.10 totalmole of reactants per cubic centimeters of catalyst per minute.

11. In a process for the production of a diene by interaction of analpha,beta-olefinically unsaturated ketone having a linear group of atleast four contiguous carbon atoms joined together by aliphaticcarbon-to-carbon bonds including the carbon atom of the carbonyl groupand an alcohol having at least one atom of hydrogen directly linked tothe carbon atom to which the hydroxyl group is bonded the improvementconsisting of effecting such reaction by passing a gaseous mixturecomprising said reactants into contact with a solid catalyst essentiallycomprising an oxide of an element of group II of the periodic table ofthe elements at a temperature of from about 200 C. to about 500 C.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,410,445 Ipatieflf et al. Nov. 5, 1946 2,421,361 Toussaint etal. May 27, 1947 2,423,681 Butterbaugh et al. July 8, 1947 2,502,431Copenhaver et al. Apr. 4, 1950 2,502,432 Copenhaver et al. Apr. 4, 1950FOREIGN PATENTS Number Country Date 28,459 Holland Nov. 16, 1932

1. IN A PROCESS FOR THE PRESPARTION OF A METHYLPENTADIENE BY INTERACTIONOF MESITYL OXIDE AND AN ALCOHOL, PASSING A GASEOUS MIXTURE COMPRISINGMESITYL OXIDE AND ISOPROPYL ALCOHOL INTO CONTACT WITH A SOLID CATALYSTESSENTIALLY COMPRISING ZINC OXIDE AND AN ADSORPTIVE ALUMINA COMPRISINGPREDOMINANTLY A MEMBER OF THE GROUP CONSISTING OF ALUMINA ALPHAMONOHYDRATE, GAMMA ALUMINA, AND MIXTURES THEREOF, AND RECOVERING AMETHYLPENTADIENE FROM THE REACTION PRODUCTS.